(1) Field of the Invention
The present invention relates to dual propeller drive systems and more particularly to a device for converting a single drive shaft to a multi-propeller drive system.
(2) Description of the Prior Art
As is well known in the art, dual propeller systems provide for greater maneuverability and for greater directional stability against wind and water currents than do single propeller drive systems. Increased maneuverability and directional stability make navigation through crowded waters easier and facilitates docking of a ship. Dual propeller drive systems obtain this greater maneuverability and directional stability by individually controlling propeller speed in a such manner as to allow the propellers to rotate at different speeds. Rotating the propellers at different speeds enables the ship to change its course without having to change the position of the propellers or the position of a rudder.
While various conventional arrangements have been developed to obtain the benefit of individually controllable propeller speeds, such arrangements generally suffer from one or more disadvantages. For example, some of these arrangements use a separate engine and transmission system for each propeller. This generally increases the size, weight and expense of the system and requires a corresponding increase in the amount of time and expense required to maintain the system. Other arrangements, such as that described in U.S. Pat. No. 3,112,728, use a single engine with separate transmission systems for each propeller. However, such dual transmission arrangements suffer from the added size, expense, and required maintenance associated with a second transmission system.
A dual propeller drive system using a single transmission is described in U.S. Pat. No. 3,922,997. However, the single transmission system of U.S. Pat. No. 3,922,997 requires separate gear sets, clutch assemblies and associated control elements for each propeller drive shaft. The use of separate gear sets, clutches and control elements generally increases the size, expense, complexity, and/or required maintenance of the propeller drive systems. None of the currently available devices or methods implement a multi-propeller drive system that allows the speed of each propeller to be independently controlled without using relatively expensive and complex equipment or a separate engine and transmission system for each propeller.